Magnetic material



Patented July 25, 1933 UNITED STATES PATENT OFFICE HANS SCHULZ, OF GHARLOTTENBUBG, BERLIN, GERMANY, ASSIGNOR '10 SIEMENS AND HALSKE AKTIENGESE'LLSCHAET, OF SIEMENSSTADT NEAR BERLIN, GERMANY, A.

GERMAN COMPANY MAGNETIC MATERIAL No Drawing. Application filed April 28, 1932, Serial No. 608,138, and in Germany May 20, 1931.

The present invention relates to magnetic materials and more particularly to methods of and means for reducing energy losses in cores containing such materials.

It is customary, in order to reduce energy losses in electrormagnetic cores comprising magnetic materials, to use these materials either in the form of laminatlons or sheets, or in the form of finely divided particles or dust, the laminations or partlcles in both cases being insulated from each other in a suitable manner.

Furthermore, in order to improve the properties of cores comprising such materials, it is usually necessary to sub3ect the completely assembled cores to a heat treatment at relatively high temperatures. In order to prevent direct metallic contact between the individual laminations, or dust particles, the laminations or particles are individually insulated with an insulating material able to withstand the temperature of the heat treatment. A number of refractory materials which have hitherto been used for this purpose, such as magnesia, zinc oxide kaolin, sodium silicate, iron or nickel halides, are unable to satisfactorig withstand temperatures above about 600 An object of the present invention is to provide an efficient and simple method of insulating sheets or dust particles of magnetic materials with an insulating material capable of withstanding temperatures above 600 and up to red heat of these materials. In pursuance of this object, the sheets or the particles of magnetic materials are first coated with a film or thin layer of metallic copper, for instance by electroplating or, preferably, by simply immersing the materials in copper sulphate. This film or layer of copper is then converted into copper oxide which is a refractory insulating material. This may be accomplishcd simply by giving the material the usual heat treatment. The temperature of this treatmentdepends upon the magnetic material in quescombined heat treatment and cooling, the

metallic cop er film is transformed into an adherent re ractory insulating film of copper oxide. The methods of the present invention are especially suitable for treating magnetic materials having around or less of nickel. They may be emplo ed in connection with a wide range of wellown magnetic alloys.

What is claimed is:

1. A method of electrically insulating magnetic material which comprises coating the material with a film of metallic copper, aid converting the copper into copper ox- 1 e.

'2. Method as defined in claim 1 in which the copper film is caused to adhere to the particles of magnetic material by submersmg them in copper sulphate.

3. Method as defined in claim 1 further characterized-in this that the metallic co per is converted into copper oxide by subecting the magnetic material to a heat treatment above a red heat.

4. Finely divided ma netic material having-the particles thereo individually coated with copper oxide.

5 A method of preparing magnetiecores wh1c h comprises copper plating divided portions of magnetic material, givin the material a heat treatment for the com ined purpose of improving the magnetic propertles and converting the copper to copper oxlde, and employing the material thus made to constitute the cores.

6. A ma netic core consisting of finely divided fpartlcles of ferromagnetic material insulate from one another by adherent coat- 

